1. Field of the Invention
This invention relates generally to a magnetic sensor, and more particularly to a magnetic head and a magnetic memory used for computers and information processing units.
2. Description of the Related Art
Magnetic recording media have been predominantly magnetic disks and magnetic tapes. They are manufactured by forming a thin magnetic film on an Al substrate or a resin tape. A magnetic head utilizing an electromagnetic conversion operation is used in order to write and read magnetic information to and from these magnetic media. This magnetic head comprises a write portion for writing the magnetic information to the recording medium and a read portion for reading out the magnetic information from the recording medium. A so-called "induction type head", which comprises a coil and magnetic poles that wrap the coil from above and below and are electrically connected to the coil, is generally used for the write portion. Magneto-resistance effect (MR) heads have been proposed recently for the read portion so as to cope with the magnetic information having a high recording density. Among the MR heads, those heads which utilize the gigantic magneto-resistance effect (GMR) are well known nowadays.
Recently, a magnetic sensor using a ferromagnetic tunnel magneto-resistance effect (spin tunnel magneto-resistance effect: TMR) has been proposed for a magnetic memory as described in JP-A-10-4227. This TMR can obtain a greater resistance change ratio by causing a current to flow in a direction of film thickness of the magneto-resistance effect film than the conventional magneto-resistance effect devices such as the GMRs which cause a current to flow in a direction of the main plane of the magneto-resistance effect film.
According to the construction described in JP-A-10-4227, however, an upper electrode stack 30 comprising at least a free ferromagnetic layer 32 and a protective layer 34 must be formed inside a contact hole defined in an insulating layer 40. Therefore, production is difficult, and film quality and film thickness of each layer inside the contact hole are likely to fluctuate from a desired level.